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Short Term Debt (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Oct. 11, 2018 | Mar. 23, 2018 | Mar. 07, 2018 | Mar. 22, 2017 | Mar. 08, 2017
Revolving Credit Facility [Member] | TECO Energy Inc. and TECO Finance Inc. [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  | $ 400 | $ 300 |
Line of Credit Facility, Additional Amount Available From Request |  |  |  |  | 100 |  |
Accounts Receivable Revolving Credit Facility | Tampa Electric Division [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  | $ 150 |  |  |
Line of Credit Facility, Expiration Date | Mar. 22, 2021 | Mar. 23, 2018 |  |  |  |  |
Finance Term Credit Facility [Member] | Tampa Electric Division [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  | $ 300 |  |  |  |
Finance Term Credit Facility [Member] | TECO Energy Inc. and TECO Finance Inc. [Member] |  |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  | 500 |  | $ 400
Line of Credit Facility, Expiration Date | Mar. 08, 2019 |  |  |  |  |  |
Line of Credit Facility, Additional Amount Available From Request |  |  |  |  | $ 100 |  |

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- Definition Date the credit facility terminates, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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